In an image forming apparatus such as a copying machine, a light exposing means is reciprocably moved along a document glass by the operation of a scanning motor, the document glass is scanned with light during the forward movement to read out an image of a document, and a read-out image is formed on a copying sheet as an image formation medium. As a scan motor use is made of a pulse motor.
The light exposure means includes, as constituent elements, a light exposure lamp and a carriage with the light exposure light mounted thereon. The carriage is reciprocably moved along the document glass and coupled to a shaft of the scan motor through a power transmission mechanism, such as a belt and wire, and moved in reciprocatory motion upon receipt of a power of the scan motor.
The light exposure lamp has a limited service life and, upon burning-out, cannot read out an image on the document in which case a copying sheet emerges as a solid black image.
During a continuous copying operation performed in a continuous copying mode in particular, there are sometimes the cases where the light exposure lamp will burn out. If, in this case, a printing operation is continued to a last end in spite of the burning-out of the light exposure lamp, a developing agent and copying sheet are consumed in a waste manner.
The present invention is achieved with the above-mentioned situation in mind and it is accordingly the object of the present invention to provide an image forming apparatus and method of controlling the apparatus which, when a light exposure lamp burns out, can immediately detect it and avoid a waste consumption of a developing agent and image formation medium.
An image forming apparatus of the present invention comprises a document glass on which a document is placed, a light exposure lamp for exposing the document glass with light, a color reference member for shading correction which is provided at a non-document-placing area of the document glass, moving means for moving the light exposure lamp along the document glass, image signal outputting means for receiving reflected light from the document glass under the light exposure and movement of the exposure lamp and outputting an image signal corresponding to that light receiving amount, and deciding means for deciding whether or not the light exposure lamp burns out by comparing an output of the image signal outputting means involved when a light exposing position of the light exposure lamp corresponds to the color reference member with an initially set value.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.